Download Codominance and Incomplete Dominance Problems

Name_______________________ Period:________
HUMAN GENETICS PRACTICE WORKSHEET #3
1. Explain the difference between incomplete and codominance.
Codominance: heterozygous individuals express both traits, ex: a chicken with black feather breeds with a white chicken to produce
offspring that have BOTH white and black feathers
Incomplete Dominance: heterozygous individuals show a blended phenotyp, ex: crossing a white and pink flower results in pink
offspring
Co-Dominance Problems
2. In some chickens, the gene for feather color is controlled by codominance. The allele
for black is B and the allele for white is W. The heterozygous phenotype is known as
erminette (black and white spotted).
a. What is the genotype for black chickens? ____
b. What is the genotype for white chickens? ____
c. What is the genotype for erminette chickens? ____
3. If two erminette chickens were crossed, what is the probability that:
a. They would have a black chick? ____%
b. They would have a white chick? ____%
Parents: ____ X ____ Show the Punnett Square:
4. A black chicken and a white chicken are crossed. What is the probability that they will
have erminette chicks? ____%
Parents: ____ X ____ Show the Punnett Square:
5. Roan is a coat color found in many animals, including horses, cattle and dogs. It is
defined generally as an even mixture of white and red hair. What offspring are expected
from mating a roan bull and a roan cow?
6. What phenotypes would you expect from a cross between a red bull and a white cow?
7. Two short-tailed (Manx) cats are bred together. They produce three kittens with long
tails, five short tails, and two without any tails. From these results, how do you think tail
length in these cats are inherited? Show the genotypes for both the parents and the
offspring to support your answer.
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Incomplete Dominance Problems
1. In snapdragons, flower color is controlled by incomplete dominance. The two alleles
are red (R) and white (w). The heterozygous genotype is expressed as pink.
a. What is the phenotype of a plant with the genotype RR? ___________
b. What is the phenotype of a plant with the genotype ww? ___________
c. What is the phenotype of a plant with the genotype Rw? ___________
2. A pink-flowered plant is crossed with a white-flowered plant. What is the probability
of producing a pink-flowered plant? ____%
Parents: ____ X ____ Show the Punnett Square:
3. What cross will produce the most pink-flowered plants? Show a punnett square to
support your answer.
Parents: ____ X ____ Show the Punnett Square:
4. In Andalusian fowls, black individuals (BB) and white individuals (ww) are
homozygous.
A homozygous black bird is crossed with a homozygous white bird. The offspring are all
bluish-gray. Show the cross as well as the genotypes and phenotypes of the parents and
offspring.
5. What results if a black individual is crossed with a bluish-gray individual? (SHOW
YOUR WORK)
6. If two bluish-gray individuals were crossed, what would be the ratios for both
phenotype and genotype of the offspring?
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Codominance (Blood types)
Human blood types are determined by genes that follow the CODOMINANCE
pattern of inheritance. There are two dominant alleles A and B) and one
recessive allele o.
Blood Type
(Phenotype)
Genotype
Can donate blood to:
Can receive blood from:
O
oo
A,B,AB and O
(universal donor)
O
AB
AB
AB
A,B,AB and O
(universal receiver)
A
AA or Ao
AB, A
O,A
B
BB or Bo
AB,B
O,B
1. Write the genotype for each person based on the description:
a.
b.
c.
d.
e.
f.
g.
Homozygous for the “B” allele
Heterozygous for the “A” allele
Type O
Type “A” and had a type “O” parent
Type “AB”
Blood can be donated to anybody
Can only get blood from a type “O” donor
______
______
______
______
______
______
______
2. Pretend that Brad Pitt is homozygous for the type B allele, and Angelina
Jolie is type “O.” What are all the possible blood types of their baby?
(show your work)
3. Draw a Punnett square showing all the possible blood types for the
offspring produced by a type “O” mother and an a Type “AB” father
4. Mrs. Clink is type “A” and Mr. Clink is type “O.” They have three children
named Matthew, Mark, and Luke. Mark is type “O,” Matthew is type “A,”
and Luke is type “AB.” Based on this information:
a. Mr. Clink must have the genotype ______
b. Mrs. Clink must have the genotype ______ because ___________
has blood type ______
c. Luke cannot be the child of these parents because neither parent
has the allele _____.
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5. Two parents think their baby was switched at the hospital. Its 1968, so
DNA fingerprinting technology does not exist yet. The mother has blood
type “O,” the father has blood type “AB,” and the baby has blood type “B.”
a. Mother’s genotype: _______
b. Father’s genotype: _______
c. Baby’s genotype: ______ or ________
d. Punnett square showing all possible genotypes for children
produced by this couple
e. Was the baby switched?
6. Two other parents think their baby was switched at the hospital. The
mother has blood type “A,” the father has blood type “B,” and the baby has
blood type “AB.”
a. Mother’s genotype: _______ or ________
b. Father’s genotype: _______ or ________
c. Baby’s genotype: ______
d. Punnett square that shows the baby’s genotype as a possibility:
e. Was the baby switched?
7. Based on the information in this table, which man could not be the father
of the baby? Justify your answer with a Punnett square.
Name
Blood Type
Mother
Type A
Baby
Type B
The Postman
Type O
The UPS driver
Type AB
The waiter
Type A
The cable guy
Type B
8. Based on the information in this table, which man could not be the father
of the baby? Justify your answer with a Punnett square.
Name
Blood Type
Mother
Type O
Baby
Type A
Pharmacist
Type O
Hairdresser
Type AB
Cabdriver
Type A
Flight attendant
Type B
9. Explain why blood type data cannot prove who the father of a baby is, and
can only prove who the father is not.
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X-linked Traits
In fruit flies, eye color is a sex linked trait. Red (XR) is dominant to white (Xr).
1. What are the sexes and eye colors of flies with the following genotypes:
a. X R X r
_________________
b. X R Y _________________
c. X R X R
_________________
r
d. X Y _________________
2. What are the genotypes of these flies:
a. white eyed, male ____________
b. red eyed female (heterozygous) ________
c. white eyed, female ___________
d. red eyed, male ___________
3. Show the cross of a white eyed female X r X r with a red-eyed male X R Y .
4. Show a cross between a pure red eyed female and a white eyed male.
a. What are the genotypes of the parents ___________&
_______________
b. How many are white eyed, male___
c. How many are white eyed, female ___
d. How many are red eyed, male ____
e. How many are red eyed, female ____
5. Show the cross of a red eyed female (heterozygous) and a red eyed male.
a. What are the genotypes of the parents? ___________ &
________________
b. How many are white eyed, male___
c. How many are white eyed, female ___
d. How many are red eyed, male ____
e. How many are red eyed, female ____
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6. In humans, hemophilia is a sex linked trait. Females can be normal, carriers,
or have the disease. Males will either have the disease or not (but they won’t
ever be carriers)
= female, normal
= male, normal
= female, carrier
= male, hemophiliac
= female, hemophiliac
a. Show the cross of a man who has hemophilia with a woman who is a
carrier.
b. What is the probability that their children will have the disease?
__________
7. A woman who is a carrier marries a normal man. Show the cross.
a. What is the probability that their children will have hemophilia?
b. What sex will a child in the family with hemophilia be?
8. A woman who has hemophilia marries a normal man.
a. How many of their children will have hemophilia, and what is their
sex?
In cats, the gene for calico (multicolored) cats is codominant. Females that
receive a B and an R gene have black and orange splotches on white coats.
Males can only be black or orange, but never calico.
Here’s what a calico female’s genotype would look like. X B X R
9. Show the cross of a female calico cat with a black male.
a. What percentage of the kittens will be black and male? _________
b. What percentage of the kittens will be calico and male? _________
c. What percentage of the kittens will be calico and female? _________
10. Show the cross of a female black cat, with a male orange cat.
a. What percentage of the kittens will be calico and female? _____
b. What color will all the male cats be? _____
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